Is it a legal requirement for a website to have alt tags for all images?

[RachelBev]

Someone told me it is a legal requirement for a website to have alt tags on all of their images. Is this right? Or is this bad for SEO?

[MattAntonino]

Most SEOs I know don't know this but yes, some sites are legally required to have alt text. However, they are government sites, those who accept federal dollars or anyone who's tied to the Electronic and Information Technology Accessibility Standards under section 508 of the Rehabilitation Act of 1973, (“508 Standards”).

You can read more about these accessibility requirements here: http://www.access-board.gov/guidelines-and-standards/communications-and-it/about-the-ict-refresh/proposed-rule/ii-executive-summary

While alt text is not required for a standard commercial or informational business (as far as I know), it does help with long tail traffic, though not always the kind that converts. I would want alt text on a clothing store's images but not necessarily on a page about eye surgery. (People are unlikely to hire a doctor based on a nice photo.)

[CommT]

I think it depends on where the website is - in the UK, it is a requirement to make sure that disabled people have the same or as similar as possible experience online as anyone else. Alt tags make it easier for the blind (amongst other groups of people) to understand the context of a website - a picture tells a thousand words and all that!

I personally think its worth doing (though there are some missing on my site for various reasons) as even if you don't believe any of your visitors are using screen readers I bet some of them actually are.

In the late 90s/early 00s the well known British supermarket, Tesco redeveloped their website to be accessible (not just Alt tags), and saw a staggering increase in sales and conversions as a result. I can't remember the exact figure but it was pretty impressive.

So I guess I'm saying there are other reasons besides SEO and legal to implement accessibility features into your site - fundamental business reasons! Making more money. (though of course the cost must be weighed up against the benefit just like anything else).